Pure and fast is certainly feasible -- you don't always need to use unsafe bytestrings for example. Laziness makes performance hard to predict because you have

Pure and fast is certainly feasible -- you don't always need to use unsafe bytestrings for example. Laziness makes performance hard to predict because you have no clue when something will get evaluated -- there's no contract with the compiler. Maybe one day some group of really smart people will figure out how to take advantage of that to write compilers that produce really fast code, but I think language-wide laziness is not a feature bound for mainstream languages. Targeted laziness? Probably, it's very useful for expressing data structures. But not everywhere by default. In any case, I don't think people are trying to be disingenuous. Haskell is, or can be, all three of those things. It's just very hard to get them all at the same time.